Digital signal processor update of single channel strength signal

ABSTRACT

A method and system of periodically measuring the signal strength fluctuations in a wireless connection between a portable computer system and a wireless network. The portable computer system has a main processor and a DSP (digital signal processor). The DSP receives instructions from the main processor for controlling the periodic measuring, and subsequent thereto is placed in low power mode. The main processor is placed into a low power mode after sending the instructions. The DSP periodically awakens to measure the signal strength fluctuations while the main processor remains in a low power mode. When the signal strength fluctuation is unacceptable, this triggers the DSP to awaken the main processor. When the signal strength fluctuation is acceptable, the DSP returns to a low power state until the next periodic measuring.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of U.S. patent application Ser. No.09/847,768, entitled “Direct Digital Signal Processor Control ofMulti-Channel Scan for Re-Establishing Connections in a WirelesslyNetworked Device,” by C. Skinner, J. Brown, and W. Wong, filed May 1,2001, now U.S. Pat. No. 6,901,276, assigned to the assignee of thepresent invention and hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to portable computer systems such aspersonal digital assistants or palmtop computer systems. Morespecifically, the present invention relates to portable computer systemsthat are configured with wireless (radio) communication functionality.

BACKGROUND OF THE INVENTION

As the continuing advances in technology have enabled the furtherminiaturization of the components required to build computer systems,new categories of computer systems have been created. One of the newercategories of computer systems developed has been the portable, handheld, or “palmtop” computer system, referred to as a personal digitalassistant or PDA. Other examples of a palmtop computer system includeelectronic address books, electronic day planners, electronic schedulersand the like.

A palmtop computer system is a computer that is small enough to be heldin the user's hand and as such is “palm-sized.” As a result, a palmtopis readily carried about in the user's briefcase, purse, and in someinstances, in the user's pocket. By virtue of its size, the palmtopcomputer, being inherently lightweight, is therefore exceptionallyportable and convenient.

Continuing miniaturization has provided for the development ofadditional functionality, which can be incorporated into some portablecomputer systems. One such additional functionality incorporated intosome portable computer systems has been wireless (radio) capability.Some portable computer systems are equipped with radio transceivers(receiver/transmitter) that provide two way communication between awireless communications network and the portable computer system.Further, in addition to the main processor, the portable computer systemmay also include a DSP (digital signal processor), adapted forprocessing of data to be transceived. The DSP performs some of thecommunication processes that would have been performed by the mainprocessor.

Generally, most portable computer systems are powered by disposable orrechargeable batteries. Because the reduced size of the portablecomputer system, such that it is deemed “palm-sized,” predicates thevolume of energy which may be stored within, smaller batteries are beingutilized to comply with the diminutive size of the portable computersystem. Further, the portable computer system's power consumption is asignificant consideration in reducing the rate with which the batterieseither need to be replaced or recharged. Accordingly, portable computersystems are enabled to be placed into a minimum or low power mode, suchas a sleep mode or a deep sleep mode, while the system is not processinga specific function or particular operation.

Until recently, when communication occurred between the portablecomputer system and a wireless network, the portable computer system wasaware of an expected transmission of data. For example, when data wasbeing wirelessly transceived by the portable computer system, is was inresponse to a request by the portable computer system. Accordingly, theportable computer system was purposefully placed into a transceivingstate when a transmission was anticipated or desired, but otherwise wasnot in a transceiving mode.

Because of the ever increasing complexity within the portable computersystem, the portable computer system is frequently being implemented inapplications that require continuous transceiving readiness, much like acellular telephone. For example, when a cellular telephone is poweredup, it is enabled to receive calls at any time. By the same token, aportable computer system is able to receive, or transmit, data orinformation nearly any time the transceiver is powered up, regardless ofwhether other components are in a sleep (low power consumption) mode.

It is desirable for the portable computer system (with a wirelesstransceiver) to remain “in coverage” when the transceiver is powered up,such that uninterrupted wireless communication is enabled. However, dueto, in part, its portability, there may be instances when the signalstrength may fluctuate such that the communicative link between theportable computer system and the wireless network is lost. Additionally,dependent upon the amount of signal strength fluctuation, the portablecomputer system may entirely lose the communication link, so as to beconsidered “out of coverage.” For example, the portable computer systemhas, while in one location, an established connection utilizing aparticular broadcast channel of a network. Subsequent to or duringrelocation, the signal strength of that channel may fluctuate such thatthe communication signal may be lost.

Currently, during signal strength monitoring, the radio components arepowered up for checking and then powered down afterward, or the radiocomponents are powered up continuously, which has an adverse affect onthe power supply of the portable computer system. Additionally, the mainprocessor is commonly activated during this monitoring, which is also asubstantial drain on the portable computer system's power supply.

SUMMARY OF THE INVENTION

Thus, a need exists for a method and system for providing periodicmonitoring of the strength of a communication signal being transceivedwithout undue depletion of the retained power supply within a portablecomputer system. An additional need exists for a method and system thatfills the above listed need and which further provides for an allowablerange of signal strength fluctuation before causing the main processorto acquire a new communication channel over which data may be received.The present invention provides a novel solution to these and otherneeds. These and other objects and advantages of the present inventionwill no doubt become obvious to those of ordinary skill in the art afterhaving read the following detailed description of the preferredembodiment, which are illustrated in the various figures.

The present invention pertains to a method and system for providingperiodic signal strength monitoring without unduly depleting the powersupply within a portable computer system. In one embodiment, thewireless network is a Mobitex wireless communication system, but coulduse any well known wireless communication medium. The present inventioncan be implemented when the portable computer system is communicatingwith a wireless network and the strength of the transceiving signal isfluctuating, such that the fluctuation may have a detrimental effect onthe communication link.

The present invention can also be implemented during those periods whenthe portable computer system is out of coverage, monitoring the signalstrength and consistency of other broadcast network channels consideredfor acquiring a new signal.

In one embodiment of the present invention, the portable computer systemhas a main processor and a DSP (digital signal processor). The mainprocessor sends a command to the DSP which includes the channel to scan,two fluctuation threshold levels, and a sleep time. The main processoris put into a low power (sleep) mode, thereby conserving retained power.The DSP is also placed into a low power (sleep) mode, also conservingretained power. In accordance with the current embodiment, the internaltimer of the DSP periodically (as specified by the sleep time) awakensthe DSP to monitor the RSSI (radio signal strength indication) forfluctuation during communication. If the DSP detects fluctuation thatexceeds the threshold levels, the DSP will interrupt or awaken the mainprocessor to act upon this data. If no threshold crossing fluctuationsare detected, the DSP will return to the low power mode until the nextspecified time for monitoring the RSSI.

The present invention provides a method and system for periodic signalstrength monitoring without unduly depleting the power supply within aportable computer system. The present invention further provides, in oneembodiment, a method and system that achieves the above listedaccomplishment and which provides for an allowable range of signalstrength fluctuation without unnecessarily activating the mainprocessor. The present invention further provides a method and systemthat achieves the above listed accomplishments and which does so whilein a low-power (sleep) mode, thereby inherently saving battery power.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention:

FIG. 1 is a block diagram of an exemplary network environment includinga portable computer system in accordance with one embodiment of thepresent invention.

FIG. 2A is a top side perspective view of a portable computer system inaccordance with one embodiment of the present invention.

FIG. 2B is a bottom side perspective view of the portable computersystem of FIG. 2A.

FIG. 3A is a top side perspective view of a portable computer systemhaving a hinged front cover in accordance with one embodiment of thepresent invention.

FIG. 3B is a bottom side perspective view of the portable computersystem of FIG. 3A.

FIG. 4 is a block diagram of an exemplary portable computer system uponwhich embodiments of the present invention may be practiced.

FIG. 5 is a flowchart showing steps in a process for periodic measuringof channel signal strength during an established wireless communicationlink between a portable computer system and a wireless network inaccordance with one embodiment of the present invention.

FIG. 6 is a linear representation of threshold limits utilized by thepresent invention when implemented for RSSI monitoring, in accordancewith one embodiment of the present invention.

DETAILED DESCRIPTION

A method and system for periodically measuring channel signal strengthduring an established wireless communication link between a portablecomputer system and a wireless network are described. In the followingdescription, for purposes of explanation, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. It will be obvious, however, to one skilled in the art thatthe present invention may be practiced without these specific details.In other instances, well-known structures and devices are shown in blockdiagram form in order to avoid obscuring the present invention.

Notation and Nomenclature

Some portions of the detailed descriptions, which follow, are presentedin terms of procedures, steps, logic blocks, processing, and othersymbolic representations of operations on data bits that can beperformed on computer memory. These descriptions and representations arethe means used by those skilled in the data processing arts to mosteffectively convey the substance of their work to others skilled in theart. A procedure, computer executed step, logic block, process, etc., ishere, and generally, conceived to be a self-consistent sequence of stepsor instructions leading to a desired result. The steps are thoserequiring physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated in a computer system. It has provenconvenient at times, principally for reasons of common usage, to referto these signals as bits, values, elements, symbols, characters, terms,numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present invention,discussions utilizing terms such as “determining” or “scanning” or“waking” or “initiating” or “sending” or “receiving” or “transceiving”or “triggering” or “displaying” or “updating” or “measuring” and thelike, refer to the action and processes of a computer system or similarelectronic computing device, that manipulates and transforms datarepresented as physical (electronic) quantities within the computersystem's registers and memories into other data similarly represented asphysical quantities within the computer system memories or registers orother such information storage, transmission or display devices.

The present invention is discussed primarily in the context of aportable computer system, such as a palmtop or personal digitalassistant. However, it is appreciated that the present invention can beused with other types of devices that have the capability to access sometype of central device or central site, including but not limited topalmtop computer systems.

Exemplary Network Environment

FIG. 1 is a block diagram of an exemplary network environment 50including a portable computer system 100 in accordance with oneembodiment of the present invention. Portable computer system 100 isalso known as a palmtop or palm-sized computer system, a hand-helddevice, a personal digital assistant (PDA), or a personal informationdevice (PID). In one embodiment, portable computer system 100 has theability to transmit and receive data and information over a wirelesscommunication interface (e.g., a radio interface).

In the present embodiment, base station 32 is both a transmitter andreceiver base station, which can be implemented by coupling it into anexisting public telephone network 34. Implemented in this manner, basestation 32 enables portable computer system 100 to communicate with aproxy server computer system 36, which is coupled by wire to theexisting public telephone network 34.

Furthermore, proxy server computer system 36 is coupled to the Internet52, thereby enabling portable computer system 100 to communicate withthe Internet 52. Coupled with Internet 52 are multiple computer systems(e.g., servers) exemplified by computer system 38. When communicatingwith a Web site over Internet 52, protocols such as CTP (CompactTransport Protocol) and WAP (wireless access protocol) and markuplanguages such as CML (Compact Markup Language) and WML (wireless markuplanguage) can be used by portable computer system 100 in the presentembodiment.

It should be appreciated that within the present embodiment, one of thefunctions of proxy server 36 is to perform operations over the Internet52 on behalf of portable computer system 100. For example, proxy server36 has a particular Internet address and acts as a proxy device forportable computer system 100 over the Internet 52.

It should be further appreciated that other embodiments of acommunications network, planned or envisioned, may be utilized inaccordance with the present invention. For example, a wirelessconnection may be made from portable computer system 100 either directlyto the Internet 52 or directly to computer system 38. It is alsoappreciated that portable computer system 100 may be coupled to computersystem networks other than the Internet 52, such as an Intranet, localarea network, or the like.

The data and information that are communicated between base station 32and portable computer system 100 are the same type of information anddata that can conventionally be transferred and received over a wirelesscommunication interface. It should be appreciated that one embodiment ofa wireless communication system in accordance with the present inventionis the Mobitex wireless communication system.

Exemplary Palmtop Platform

FIG. 2A is a perspective illustration of the top face 100 a of oneembodiment of portable computer system 100. The top face 100 a containsa display screen 105 surrounded by a bezel or cover. A removable stylus80 is also shown. The display screen 105 is a touch screen able toregister contact between the screen and the tip of the stylus 80. Thestylus 80 can be of any material to make contact with the screen 105.The top face 100 a also contains one or more dedicated and/orprogrammable buttons 75 for selecting information and causing thecomputer system to implement functions. The on/off button 95 is alsoshown.

FIG. 2A also illustrates a handwriting recognition pad or “digitizer”containing two regions 106 a and 106 b. Region 106 a is for the drawingof alphabetic characters therein (and not for numeric characters) forautomatic recognition, and region 106 b is for the drawing of numericcharacters therein (and not for alphabetic characters) for automaticrecognition. The stylus 80 is used for stroking a character within oneof the regions 106 a and 106 b. The stroke information is then fed to aninternal processor for automatic character recognition. Once charactersare recognized, they are typically displayed on the screen 105 forverification and/or modification.

Still referring to FIG. 2A, RSSI (radio signal strength indicator) 2001is shown as disposed upon the upper right corner of display screen 105,in one embodiment of the present invention. In another embodiment, RSSI2001 may be disposed nearly anywhere upon portable computer system 100,and not necessarily disposed within display screen 105. In this example,RSSI 2001 is a visual indicator using discreet lights, for example, toindicate signal strength. In this example, the stronger the signal, thegreater the number of lights that will be illuminated. In anotherembodiment, a single light may be implemented to indicate RSSIfluctuations, such that when the signal strength is acceptable, thelight is illuminated. In yet another embodiment, there may be twodifferently colored lights, for example, a red and a green light, suchthat the green light would be illuminated to indicate acceptable signalstrength fluctuation. Accordingly, a red light would be illuminated toindicate an unacceptable signal strength fluctuation. In anotherexample, the lights may be nearly any other shape and or size.

It should further be appreciated that in another embodiment, RSSI 2001may be an audible indicator, where, in one example, a sequence of beepsmay indicate signal strength and in another example, the louder a tone,a greater signal strength is indicated and the quieter the tone, aweaker signal strength is indicated. In yet another embodiment, RSSI2001 may be a motion activating device, such that the signal strength isindicated by the intensity of a vibration, such that an intense motionindicates a strong signal strength.

FIG. 2B illustrates the bottom side 100 b of one embodiment of thepalmtop computer system that can be used in accordance with variousembodiments of the present invention. Battery storage compartment door90 is shown. In one embodiment, an internal antenna (not shown) may bepresent and coupled with communication circuit 135 of FIG. 4. Acommunication interface 180 and an infrared port 64 are also shown. Inone embodiment, communication interface 180 is a serial port. In anotherembodiment, communication interface 180 can be a parallel port, a USB(universal serial bus), an IEEE 1394 connection, and the like. In oneembodiment, infrared communication mechanism 64 is compliant with theIrDA (Infrared Data Association) standard and protocol.

FIG. 3A is a perspective illustration of the top face 100 c of oneembodiment of portable computer system 100. The top face 100 a containsa display screen 105 surrounded by a bezel or cover. A removable stylus80 (as shown in FIG. 2A) is present, although not shown because of theviewing angle. The display screen 105 is a touch screen able to registercontact between the screen and the tip of the stylus 80. The stylus 80can be of any material to make contact with the screen 105. The top face100 c also contains one or more dedicated and/or programmable buttons 75for selecting information and causing the computer system to implementfunctions.

Still referring to FIG. 3A, front cover 175 for providing protectionagainst damage to display screen 105 is also shown. Front cover 175 isadapted to rotate about an axis, or hinge, as indicated by the arrow.Also shown is RSSI 2001 disposed upon the upper left corner of displayscreen 105. In this embodiment, a series of rectangular indicating LEDs(light emitting diodes) are used to visually indicate signal strength.In this example, the weaker the signal, less lights are illuminated andthe stronger the signal, more lights are illuminated.

FIG. 3B illustrates the bottom side 100 d of one embodiment of thepalmtop computer system that can be used in accordance with variousembodiments of the present invention. A stylus 80, an extendible antenna85, and a battery storage compartment door 89 are shown. A communicationinterface 180 and an infrared port 64 are also shown. In one embodiment,communication interface 180 is a serial port. In another embodiment,communication interface 180 can be a parallel port, a USB (universalserial bus), an IEEE 1394 connection, and the like. In one embodiment,infrared communication mechanism 64 is compliant with the IrDA (InfraredData Association) standard and protocol.

Still referring to FIG. 3B, external auxiliary card slot 140 is shown.Card slot 140 is adapted to receive compact and/or flash memory cards,e.g., SDs (secure digital cards), or MMCs (multimedia cards), or memorysticks and the like. Front cover 175 is also shown and is adapted torotate about the axis, or hinge, as indicated by the arrow.

FIG. 4 is a block diagram of one embodiment of a portable computersystem 100 upon which embodiments of the present invention may beimplemented. Portable computer system 100 is also often referred to as aPDA, a PID, a palmtop, or a hand-held computer system.

Portable computer system 100 includes an address/data bus 130 forcommunicating information, a central (main) processor 131 coupled withthe bus 130 for processing information and instructions, a volatilememory 132 (e.g., random access memory, RAM) coupled with the bus 130for storing information and instructions for the main processor 131, anda non-volatile memory 133 (e.g., read only memory, ROM) coupled with thebus 130 for storing static information and instructions for the mainprocessor 131. Portable computer system 100 also includes an optionaldata storage device 134 (e.g., auxiliary card slot 140 of FIG. 3B)coupled with the bus 130 for storing information and instructions.Device 134 can be removable. Portable computer system 100 also containsa display device 105 coupled to the bus 130 for displaying informationto the computer user.

In the present embodiment, portable computer system 100 includes asignal input/output device (transceiver) 144 providing it with thecapability for wireless communication. The transceiver 144 provides awireless radio frequency (RF) communication link between computer system100 and other devices, using any of the various RF protocols andstandards. In one embodiment, the Mobitex wireless communicationspecification is used. In another embodiment, the Bluetooth wirelesscommunication specification is used. In still another embodiment, awireless LAN (local area network) communication specification is used.It is appreciated that transceiver 144 may be integrated into portablecomputer system 100, or that transceiver 144 may be a separate componentcoupled to portable computer system using, for example, serial port 180.

It is appreciated that in another embodiment portable computer system100 may also include a telephony chipset or the like providing it withthe functionality of a cellular phone, in particular the capability totransmit and receive cellular communications. In one embodiment, thetelephony chipset is compatible with the standards for GSM and GPRS(Global System for Mobile Communications and General Packet RadioService, respectively). It is appreciated that other telephony protocolsand standards may also be used with the present invention.

In the present embodiment, portable computer system 100 of FIG. 4includes communication circuitry 135 coupled to bus 130. In oneembodiment, communication circuitry 135 is a universal asynchronousreceiver-transmitter (UART) module that provides the receiving andtransmitting circuits required for serial communication for both theserial port 180 and the infrared port 64. Communication circuitry 135also includes DSP (digital signal processor) 136 for processing data tobe transmitted or data that are received via transceiver 144.

Also included in computer system 100 is an optional alphanumeric inputdevice 106 that, in one implementation, is a handwriting recognition pad(“digitizer”). Alphanumeric input device 106 can communicate informationand command selections to main processor 131 via bus 130. In oneimplementation, alphanumeric input device 106 is a touch screen device.Alphanumeric input device 143 is capable of registering a position wherea stylus element (not shown) makes contact.

Portable computer system 100 also includes an optional cursor control ordirecting device (on-screen cursor control 143) coupled to bus 130 forcommunicating user input information and command selections to mainprocessor 131. In one implementation, on-screen cursor control device143 is a touch screen device incorporated with display device 105.On-screen cursor control device 143 is capable of registering a positionon display device 105 where a stylus element makes contact. The displaydevice 105 utilized with portable computer system 100 may be a liquidcrystal display (LCD) device, a cathode ray tube (CRT), a field emissiondisplay device (also called a flat panel CRT), or other display devicesuitable for generating graphic images and alphanumeric charactersrecognizable to the user. In the preferred embodiment, display device105 is a flat panel display.

Portable computer system 100 also includes RSSI (radio signal strengthindicator) 2001 which is coupled to communication bus 130 and is shownin FIGS. 2A and 3A. RSSI 2001 is adapted to provide a visual indicationof a particular broadcast network's channel signal strength duringperiods of transceiving.

DSP Monitoring of Fluctuation in Channel Signal Strength

The purpose of the signal strength fluctuation measurement is to provideto a user a quicker more rapid update of the current channel signalstrength. It should be appreciated that the present invention isapplicable when in coverage and when out of coverage. The somewhatlimited power resources contained within portable computer system 100(FIG. 4) are conserved by utilizing a DSP (digital signal processor) toperform the signal strength fluctuation measurements instead of havingmain processor 131 (FIG. 4) perform that task. Additionally, thetransceiving notification (signal strength) is updatable at a morefrequent rate than what the stack (running on main processor 131 of FIG.4) was able to provide without severe negative impacting of the retainedpower supply.

FIG. 5 is a flowchart of the steps in a process 500 for periodicmeasuring of signal strength fluctuation of a wireless connectionbetween portable computer system 100 (FIG. 4) and wireless network 50(FIG. 1) in accordance with one embodiment of the present invention. Inthe present embodiment, process 500 is implemented as computer-readableprogram instructions executed by portable computer system 100. For thesignificant conservation of power, portions of process 500 are performedby DSP 136 of FIG. 4 while main processor 131 (FIG. 4) remains in a lowpower mode, as will be seen.

In step 510 of FIG. 5 and with reference to FIG. 4, DSP 136 receivesfrom main processor 131 instructions for controlling the periodicmeasuring of signal strength fluctuation of a wireless connection to beperformed by DSP 136. The instructions provide the duration of aperiodic timed interval of low power entered into by DSP 136, in oneembodiment of the present invention. The instructions further provide aparticular broadcast channel frequency for DSP 136 to measure. Thefrequency to be measured for fluctuation by DSP 136 equates to thefrequency of the wireless connection. The instructions also provide anupper threshold and a lower threshold which define the range ofacceptable fluctuation of the signal strength of the wirelessconnection.

Still referring to step 510, the duration of a periodic timed intervalprovides a regulated sleep time for DSP 136. When the sleep time isover, the DSP is awakened to perform the measuring of the signalstrength fluctuation.

In step 520 of FIG. 5, with reference also to FIG. 4, once mainprocessor 131 has sent the controlling instructions regarding periodicmeasuring to DSP 136, main processor 131 is automatically placed into alow power mode (e.g., a sleep mode or a deep sleep mode). In accordancewith the present invention, main processor 131 will remain in a lowpower mode through step 570 of process 500.

In step 530 of FIG. 5 and with reference also to FIG. 4, once DSP 136has received the controlling instruction regarding periodic measuring ofsignal strength fluctuation, DSP 136 is automatically placed into a lowpower mode (e.g., a sleep mode or a deep sleep mode).

In step 540 of FIG. 5, still with reference to FIG. 4, subsequent to theexpiration of the periodic timed interval of low power mode in which DSP136 was placed, DSP 136 is awakened to measure signal strengthfluctuation of a wireless connection. In one embodiment, the duration ofthe periodic timed interval can be twenty seconds. In anotherembodiment, the duration may be fifteen seconds. In yet anotherembodiment, the duration may be for thirty seconds. It should beappreciated that the duration of periodic timed interval of low powermode is adjustable, such that a wireless connection prone to large andfrequent fluctuation may required more frequent measurement, and awireless connection having relatively constant signal strength mayrequire less frequent measuring of signal strength.

In step 550 of FIG. 5, once awakened, DSP 136 measures signal strengthfluctuation of the wireless connection, in one embodiment. It should beappreciated that DSP 136 performs the measuring of the signal strengthfluctuation while main processor 131 remains in a low power mode.

In step 560 of FIG. 5, subsequent to the measuring of fluctuation ofsignal strength, provided the measured signal strength fluctuation iswithin the range of acceptable fluctuation, as defined in step 510, DSP136 returns to a low power mode until the period timed interval of lowpower mode expires and DSP 136 is again awakened to perform signalstrength fluctuation of the wireless connection. However, when aninstance occurs when the measured signal strength fluctuation exceedsthe range of acceptable fluctuation, DSP 136 is automatically triggeredto awaken main processor 131.

In step 570, once main processor 131 has been awakened, caused by thefluctuation of signal strength exceeding the range of acceptablefluctuation, main processor 131 acts upon this data. In one embodiment,main processor 131 may switch to an alternate broadcast channel which isknown to have minimal signal strength fluctuation. In anotherembodiment, main processor may be instructed to search for an acceptablebroadcast channel with which it may continue the wireless connectionpreviously obtained.

FIG. 6 is a linear representation of the upper and lower thresholdvalues utilized during implementation of the of the present invention,in accordance with one embodiment of the present invention. The upperand lower thresholds provide a range of fluctuation so that mainprocessor 131 (FIG. 4) is not unnecessarily awakened. Because the signalstrength is affected by noise in the system, the RSSI (radio signalstrength indicator) value calculated by the DSP 136 will have somevariance. If utilizing a single threshold level, when the signalstrength is close to the threshold, the RSSI read by DSP 136 couldfluctuate around the threshold level and cause the DSP 136 tounnecessarily awaken main processor 131. To avoid this problem, mainprocessor 131 sends two threshold levels to the DSP 136. This allows fora range of threshold levels so as not to trigger the DSP to awaken mainprocessor 131.

Still referring to FIG. 6, upper threshold level UT 606 and lowerthreshold level LT 607 which define a range of acceptable fluctuationsare shown. FIG. 6 has three sections which are sections A, B, and C.Section A is to the left, section B is in the middle, and section C isto the right. Each section has two examples of signal strengthfluctuations.

For example, assume that an RSSI of 6 dB (decibels) is measured. Themain processor may, in this example, want to be informed when the signalstrength drops below an RSSI level of 5.0. Accordingly, the mainprocessor could send to the DSP thresholds that correspond to 4.5 and5.0, which is shown in UT 606 and LT 607, respectively. The DSP wouldnot awaken the main processor until the RSSI went below 4.5 dB,represented by LT 607. Conversely, if the initial RSSI were 3 dB, theDSP would not awaken the main processor until the RSSI rose above 5 dB,represented by UT 606. RSSI values between 4.5 and 5 dB would nottrigger the DSP to awaken the main processor.

Referring to section A of FIG. 6, in one example, fluctuation 620 isshown to have an initial RSSI level which is above UT 606. Duringtransceiving, 620 falls below UT 606 (5 dB) but remains above LT 607.Accordingly, fluctuation 620 does not trigger the DSP to awaken the mainprocessor.

In another example, fluctuation 622 is shown to have an initial RSSIlevel which is below UT 606 but above LT 607. During transceiving, 622drops lower but does not fall below LT 607. Accordingly, fluctuation 622does not trigger the DSP to awaken the main processor.

Referring to section B of FIG. 6, in one example, fluctuation 624 isshown to have an initial RSSI of 6 dB. During transceiving, 624 dropsbelow UT 606 and also drops below LT 607. Accordingly, fluctuation 624does trigger the DSP to awaken the main processor.

In another example, fluctuation 626 is shown to have an initial RSSIlevel which is between UT 606 and LT 607. During transceiving, 626 fallsbelow LT 607. Accordingly, fluctuation 626 triggers the DSP to awakenthe main processor.

Referring to section C of FIG. 6, fluctuation 628 is shown to have aninitial RSSI level of 3 dB which is below LT 607. During transceiving628 rises above LT 607 and continues above UT 606. Accordingly,fluctuation 628 would cause the DSP to awaken the main processor.

In another example, fluctuation 630 is shown to have an initial RSSIlevel which is below LT 607. During transceiving 630 rises above LT 607but remains below UT 606. Accordingly, fluctuation 630 would not cause atriggering of the DSP to awaken the main processor.

In summary, the present invention provides a method and system whichconserves retained power within a portable computer system whileperiodically measuring signal strength fluctuations in a wirelessconnection between a portable computer system and a wireless network. Inaccordance with the present invention, the DSP awakens periodically froma low power mode to measure signal strength fluctuation while the mainprocessor remains in a low power mode. If the measured signal strengthfluctuation is within an acceptable range, the DSP returns to a lowpower mode until the next periodic measurement. Not until anunacceptable range of fluctuation is measured, is the main processorawakened. With the main processor remaining in a low power mode duringsignal strength measurements, battery life is extended thereby reducingthe frequency with which the batteries need to be recharged or replaced.

The present invention has been described in the context of a portablecomputer system; however, the present invention may also be implementedin other devices having, for example, a main processor and a DSP(digital signal processor) that enables the main processor to be placedinto a low power mode while the DSP performs certain functions on behalfof the main processor, including those not necessarily associated withmeasuring signal strength fluctuations.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto and theirequivalents.

1. In a computer system comprising a DSP (digital signal processor) anda main processor, a method for periodically measuring signal strengthfluctuations of a wireless connection between said computer system and awireless network, said method comprising the steps of: a) receivinginstructions by said DSP from said main processor controlling saidmeasuring of said signal strength fluctuations; b) waking said DSPduring periods of transceiving, said waking caused by expiration of aperiodic timed interval of low power mode entered by said DSP; c)measuring said signal strength of said wireless connection fluctuationsduring periods of transceiving, wherein said step c) is performed bysaid DSP while said main processor remains in said low power mode; d)waking said main processor provided said fluctuation is in excess of anacceptable range; and e) returning said DSP to said low power modeprovided said fluctuation of said signal strength is within saidacceptable range.
 2. The method as recited in claim 1 further comprisingthe steps of: automatically placing said main processor in a low powermode subsequent to said step a); and automatically placing said DSPsubsequent to said step a).
 3. The method as recited in claim 1 whereinsaid instructions are for providing the duration of said periodic timedinterval of said low power mode entered by said DSP.
 4. The method asrecited in claim 1 wherein said instructions provide an upper thresholdlimit and a lower threshold limit of said wireless connection signalstrength fluctuation, wherein said upper and said lower threshold limitsare for defining said acceptable range.
 5. The method as recited inclaim 1 wherein said instructions provide a particular broadcast channelfrequency for said DSP to monitor, said frequency equating to thefrequency of said wireless connection.
 6. The method as recited in claim1 wherein said step b) further comprises the step of: b1) repeatingsteps b) and c) automatically in accordance with said periodic timedintervals of said instructions.
 7. The method as recited in claim 1further comprising the step of: f) displaying said measurement of saidfluctuation of said signal strength on a signal strength indicator,wherein said display is generated by said DSP.
 8. The method as recitedin claim 1 wherein said wireless network is a Mobitex wirelesscommunication system.
 9. A portable computer system comprising: a bus; asignal strength indicator coupled to said bus; a wireless transceivercoupled to said bus; a main processor coupled to said bus; and a DSP(digital signal processor) coupled to said bus for executing a methodfor periodically measuring the signal strength of a wireless connectionbetween said portable computer system and a wireless network, saidmethod comprising the steps of: a) receiving instructions by said DSPfrom said main processor for controlling said measuring said signalstrength for fluctuations; b) waking said DSP during periods oftransceiving, wherein said waking is caused by the expiration of adefined periodic interval of low power mode entered by said DSP; c)measuring said signal strength for said fluctuations during periods oftransceiving, wherein said step c) is performed by said DSP while saidmain processor remains in said low power mode; d) waking said mainprocessor, provided said fluctuations are in excess of an acceptablerange; and e) returning said DSP to said low power mode provided saidfluctuations are within said acceptable.
 10. The system as recited inclaim 9 and further comprising the steps of: automatically placing saidmain processor into a low power mode subsequent to said step a); andautomatically placing said DSP into a low power mode subsequent to saidstep a).
 11. The system as recited in claim 9 wherein said instructionsprovide a duration of said periodic time interval of low power modeentered by said DSP.
 12. The system as recited in claim 9 wherein saidinstructions are for providing an upper threshold limit and a lowerthreshold limit of said wireless connection signal strengthfluctuations, wherein said upper and said lower threshold levels are fordefining an acceptable range.
 13. The system as recited in claim 9wherein said instructions provide a particular broadcast channelfrequency for said DSP to measure, said frequency equating to thefrequency of said wireless connection.
 14. The system as recited inclaim 9 wherein said step b) further comprises the step of: b1)repeating said steps b) and c) automatically in accordance with saidperiodic timed intervals.
 15. The system as recited in claim 9 andfurther comprising the step of: f) displaying said measurement of saidfluctuation of said signal strength on said signal strength indicator,wherein said display is generated by said DSP.
 16. The system as recitedin claim 9 wherein said wireless network is a Mobitex wirelesscommunication system.
 17. In a portable computer system comprising a DSP(digital signal processor) and a main processor and an RSSI (radiosignal strength indicator), a method for periodically measuring offluctuation of the signal strength of a wireless connection between saidportable computer system and a wireless network, said method comprisingthe steps of: a) receiving instructions by said DSP from said mainprocessor for controlling periodic measuring of said signal strength forfluctuations; b) said DSP waking to perform said periodic measurement ofsaid fluctuations of said signal strength; c) said DSP measuring saidfluctuations of said signal strength while said main processor remainsin a low power mode; d) said DSP waking said main processor providedsaid fluctuations exceeds an acceptable range; and e) said DSP returningto said low power mode provided said fluctuations of said signalstrength are within said acceptable range.
 18. The system as recited inclaim 17 and further comprising the steps of: automatically placing saidmain processor into a low power mode subsequent to said step a); andautomatically placing said DSP into a low power mode subsequent to saidstep a).
 19. The system as recited in claim 17 wherein said instructionsprovide a duration of said periodic time intervals of said low powermode entered by said DSP.
 20. The system as recited in claim 17 whereinsaid instructions provide an upper threshold limit and a lower thresholdlimit of said fluctuation of said wireless connection signal strengthfluctuation, wherein said upper and said lower threshold limits are fordefining an acceptable range.
 21. The system as recited in claim 17wherein said instructions provide a particular broadcast channelfrequency for said DSP to measure, said frequency equating to thefrequency of said wireless connection.
 22. The system as recited inclaim 17 wherein said step b) further comprises the step of: b1) saidDSP repeating said step b) and said step c) automatically in accordancewith said periodic timed intervals.
 23. The system as recited in claim17 and further comprising the step of: f) said DSP generating a displayof said measured fluctuation of said signal strength, wherein saiddisplay is on said RSSI.
 24. The method as recited in claim 17 whereinsaid wireless network is a Mobitex wireless communication system.